Stade Francais eye Top 14 survival after 'rubbish' season
The Parisians, 14-time champions, are in 12th place in the table on 41 points having been in the league since 1997.
Perpignan are one spot and one point below them sitting in the relegation play-off berth, as they host league leaders Toulouse.
The side finishing in 13th will play the loser of the second-tier Pro D2 final, with Grenoble playing Montauban earlier on Saturday in the 'Access Match'.
Bottom of the table Vannes are on 36 points, and face a tough trip to Champions Cup winners Bordeaux-Begles, with all of the day's games kicking off at the same time adding to the drama.
"It's the match for survival," Stade Francais back-rower Romain Briatte told reporters on Thursday.
"We haven't spoken much this week.
"We want to especially agree on the actions," the 32-year-old added.
Briatte's side have won just nine league games so far this term, a stark contrast from 12 months ago when they reached the semi-finals.
"It's been a very difficult season, A rubbish season," the France flanker said.
"We were bored throughout the year," he added.
One positive for Stade Francais, owned by German-Swiss billionaire Hans-Peter Wild, who is worth $3.6 billion, is their track record against this weekend's visitors.
Castres have not won at Stade Jean-Bouin in the league since 2001 but are eyeing a spot in next week's title play-offs.
"There are 80 minutes of a fight that awaiting us," Briatte said
"Against a Castres team that will be super determined to win," he added.'Heads held high'
Perpignan, champions in 2009 with an injured Dan Carter, will be boosted by an 18th-straight sold-out crowd when they welcome Toulouse.
"I have total trust in Franck Azema to save the club," the Catalans' president Francois Riviere told L'Equipe.
"I find him determined and relaxed because he knows I don't doubt him.
"Of course Franck would have prefered an easier season but he's not going to beat himself up about it," he added.
Vannes have a slim chance of survival having been promoted for the first time ever last season.
"This season will remain etched in our memories forever," fly-half Maxime Lafage told his team-mates in a huddle after last weekend's home defeat to Pau.
"We will remember it in 10, 20 years.
"Keep your heads held high," he added.
Along with Castres, five other teams are battling it out for the play-offs.
Bayonne, La Rochelle, Clermont, Pau can make them as well as third-placed Toulon, who are guaranteed a spot but they can also reach the semi-finals in a trip to the Basque Country.
Fixtures (time GMT)
Bayonne v Toulon, Lyon v Racing 92, Montpellier v Clermont, Pau v La Rochelle, Stade Francais v Castres, Bordeaux-Begles v Vannes, Perpignan v Toulouse (all 1905)